This invention relates to a light measuring circuit.
In photographing, for example, photomicrographing, light-measuring must be made from relatively dark image to bright image, i.e. in a wide illumination range (10.sup.4 to 10.sup.5 luxes) from low to high illumination. Practically, it is very difficult to accurately measure a light over a wide range of illumination. In a conventional light measuring circuit, the incident light is detected in the form of a change of the resistance of a photoelectric converting element such as a CdS element. A photoelectric signal produced corresponding to the resistance change is applied to a logarithmic compression circuit and the incident light is taken out from the logarithmic compression circuit in the form of a voltage signal corresponding to the light intensity. When the logarithmic compression circuit is used, a high accuracy light measuring is assured over a wide illumination range, but the light measuring apparatus is expensive.